KR20000052811A - Expandable pintle wires - Google Patents

Abstract

PURPOSE: Expandable pintle wires are provided for a seam whose tendency to mark a paper web carried on a paper machine clothing belt is substantially reduced. CONSTITUTION: A pintle wire (10) for insertion through interdigitating end loops of a belt fabric or of a spiral connector, is disclosed which is expandable after insertion into the seam, for example by means of a sheath (12) which includes a thermally activated expanding agent. This is subject to heating to expand the sheath, causing the pintle wire to swell and fill voids in the seam area reducing permeability in the seam and thus reducing marking of paper webs carried by the belt.

Description

Expandable Pintle Wire {EXPANDABLE PINTLE WIRES}

Loops joined, cast or woven to the basic structure are provided at each end of the belt to form interlocking loops, either as yarns integral with the basic fabric or as casts connected or connected in the form of spiral coils to the belt's basic structure. The loops of the coil can be interlocked and aligned to allow passage of pintle wires through. However, a problem arises in which the paper web is undesirably marked in the area supported by the belt on the area where the belt end is in contact with a seam consisting of a loop and pintle wire. The reason for this marking is that the belt has greater permeability than other areas in the seam area resulting in differences in drainage.

The pintle wire itself may be monofilament, multifilament or a combination of monofilament, multifilament or yarn of yarn forming a braided yarn, a braided yarn, a cable-like yarn or a braided yarn, which may be yarn or may comprise filler fibers. Pintle wire materials are generally synthetic polymers but natural materials or minerals may be used or combinations of these materials. Pintle wires can be reinforced with resin or combined with metal wires.

The present invention relates to pintle wires used to join the ends of the belt to form seamless fabrics in paper machine covers, especially press felts, by passing through interlocking loops from each end.

1 is a cross-sectional view of a pintle wire according to the present invention.

2 and 2a show pintle wires after they pass and are inflated through opposing belts and loops.

3 is a cross-sectional view of the end seam of FIG. 2.

4 is a cross-sectional view of a second pintle wire according to the present invention.

* Code Description

10,30,40 ... pintle wire 11 ... core

12 ... sheath 20,21 ... belt end

22,23 ... Looping 24 ... Pintlewire

25 ... protrusion 31 ... yarn

32 ... core 33 ... exterior

41 ... monofilament 42 ... interior and exterior

43 ... Exterior

It is an object of the present invention to provide a seam pintle wire in which the tendency to mark paper webs carried on paper machine cloth belts is greatly reduced.

According to the invention the pintle wire consists of or comprises strands or filaments of a material which are expanded by physical or chemical means to join the end seam after introduction of the pintle wire.

The pintle wire according to the invention is a monofilament, multifilament or yarn as a combination of monofilament, multifilament or spun yarn forming a braided yarn, a braided yarn, a cable-like yarn or a braided yarn, which may or may comprise filler fibers. At least one of the filament or fibrous component is expandable after introducing the pintlewire into the belt seam formed by the interlocking loops.

The expandable component may be an expandable yarn that swells upon application of heat and includes at least one core yarn encapsulated in a resin containing a blowing agent. Multifilaments are preferred as core yarns because of the larger surface area that results in better adhesion between the resin and the resin coating, but braided yarns, braided yarns, braided yarns or cable-like yarns or even monofilaments can be used. Alternatively, the core yarn may be free and the component may be composed of a synthetic material including a blowing agent.

The expandable component contains a blowing agent that is activated by heat but the acceleration of the blowing reaction of the blowing agent may be a chemical reaction caused by contact with a source other than heat, such as water.

Other possible forms of intumescent components include pre-extended yarns that increase diameter after slowing longitudinal tension and absorbent fibers that increase dimensions by absorbing water (e.g., by superabsorbents on core filaments or hydrophilic coatings or fiber sheaths). Include. Natural fibers such as cotton or wool can be used for this purpose.

The pintle wire 10 in FIG. 1 is a monofilament comprising a core 11 made of synthetic material and a sheath 12 made of a material comprising a heat activated foaming agent. Blowing agents that produce nitrogen gas are preferred because of their non-oxidizing properties. The material of sheath 12 is partially or fully cured below the temperature at which the blowing agent is activated.

After passing through the interlocked loops of a pair of opposing belt ends, the pintle wire 10 is exposed to elevated temperatures by hot air or infrared heaters and the sheath 12 is expanded. The result is shown in FIG. Opposing belt ends 20, 21 have loops 22, 23 formed by the extension of the longitudinal warp of the belt. Pintle wires 24 pass through the loops 22 and 23 and are subsequently expanded. The expanded pintle wires 24 protrude through the gaps between adjacent loops 22 and 23 to form protrusions 25 to fill the space in the seam area, thereby reducing the permeability of the area so that the paper web is marked by seam. Reduce the tendency.

In figure 3 another pintle wire 30 is shown comprising a plurality of monofilament yarns 31 twisted or braided together. This yarn 31 has a sheath 33 and a core 32 similar to the sheath 12 of the core 11 of FIG. 1. The sheath is expandable under the same conditions as sheath 12 so that pintle wire 30 can also expand and replace pintle wire 24 of FIGS. 2 and 3.

4 shows a cabled pintle wire 40 having a core of one or more monofilaments 41, an inner sheath 42 and an outer sheath 43. The filament 41 expands in the longitudinal direction and the sheaths 42 and 43 comprise fibers wound around the core 41 and the fibers of the inner sheath 42 are wound in the opposite direction to the outer sheath 43. The fiber or core filament of the sheath comprises a blowing agent which is thermally activated as in FIG. 1 and which produces the effect shown in FIGS. 2 and 3.

Yarns used are polyester such as PET, PTT, PBT, PBN or PER, co-polyester such as PCTA, polyolefin such as PE, PP, Dyneema or Spectra (trade name), nylon 6, nylon 6.6, nylon 6.10, nylon 6.12 or nylons such as nylon 12, aramids such as Kevlar or Twaron (trade name), PBO, PEEK, polyketone, PPS, PPO, rayon, glass, metal, natural materials or combinations thereof, commonly used for pintle wires Combinations of polymer blends or fibers or yarns are possible with mono or multifilament cores of organic or inorganic polymers. Inexpensive materials such as polyester, nylon or rayon are preferred. Ferromagnetic filaments can be included in the core so that induction heat can be used to activate the blowing agent.

Another embodiment of the expandable pintle wire according to the invention is extruded yarns from thermoplastic polymer (aliphatic or partially aromatic polyamide) pellets comprising m- or p-aramid fibers and subsequently susceptible such as PVA or PEBAX (trade name). It is made by coating a yarn with a polymer sheath. When the sheath is exposed to water at the appropriate time, the yarn diameter increases by 50%.

Since the coating material must have good wear resistance, wear resistant particles or beads of polymers such as glass, ceramics, metals (magnetic materials can induce heat) or polyurethanes can be provided. Contaminant release finishes, such as fluoropolymers, may be provided on the coating or included in the coating material. The coating material may include fluorescent, luminescent, phosphorescent or light colored materials to assist in wire passage in poor light conditions. Standard ingredients such as fillers, pigments or processing aids may be included in the coating material.

The coating material actually used may be a viscous plastisol such as PVC comprising 50-60% by weight PVC resin and 40-50% by weight plasticizer and other additives. This provides excellent expandability and is a cheap material but for environmental reasons a low melting point thermoplastic such as polyolefin, polyurethane or TPU can be used. High melting point materials such as co-polyesters and co-polyamides may also be used.

Coated yarns can be flattened by rolling for use in helical seams, in which case the core yarns are hardly twisted to keep the pintle wire flat. Ideally the yarns expand almost twice in diameter.

Depending on the heat resistance of the other materials in the seam after pintlewire insertion, the yarn is exposed to a temperature of 80-200 ° C. for 3-8 seconds. Such heating can be performed using hot air or an infrared heater. In the presence of a thermosensitive material, the induced heat of the pintle wire containing ferromagnetic particles or filaments is preferred.

Typical blowing agents are AZOCEL (trade name of Fairmount Chemical Co.) which is an azodicarbonamide which decomposes at 150-200 ° C; Or azodicarbonamide kemapore 125 sold by Stepan Chemical Co. Blowing agents are added in amounts up to 15% by weight of the coating, in particular 0.2-5% by weight.

If the core is surrounded by one or more coatings, the blowing agent is preferably concentrated in the outermost coating. Coated yarns are prepared by standard coextrusion or coating techniques published in GB 2032 483 and are preferably coated under tension to prevent shrinkage during foaming.

Blowing agents (Hoechst, EP 0445708) which are not thermally active agents can be used, such as synthetic polymer polymers, sodium carbonate, citric acid mixtures and polycarbonate processing aids. This material foams on contact with water. Another material is Hynol (W.R. Grace), a foamable hydrophilic polyurethane pre-polymer derived from toluene diisocyanate that reacts with compounds containing active hydrogen atoms at room temperature to form elastic foams. The curing time is 3-6 minutes and can be accelerated by introducing a catalyst.

Another means for obtaining expandable pintle wires includes bicomponent wires that use differential shrinkage of the bicomponent yarns as in US 4551378 or EP 529506; Fibers made by Technical Absorbent's are absorbent or hydrophilic yarns (OASIS, trade name) that swell upon contact with water and pre-extended yarns that increase in diameter upon relaxation.

Claims (22)

A pintle wire consisting of a filament of material that can be foamed by physical or chemical means after the introduction of the pintle wire to connect the end seam. 2. The pintlewire of claim 1 comprising monofilament yarns. The pintlewire of claim 1, comprising a multifilament yarn. The pintle wire of claim 1, wherein the pintle wire comprises a spun yarn. 2. The pintle wire of claim 1, wherein at least a portion of the formed filaments comprise braided yarns, twisted yarns, braided yarns, cable-like yarns, and are expandable. The pintlewire of claim 1, wherein the expandable component is a yarn that swells under the action of an external stimulus. 7. The pintle wire of claim 6 wherein the expandable yarn comprises at least one core yarn encapsulated in a sheath of foam-containing resin. 8. The pintle wire of claim 7 wherein said core yarn is a multifilament. 7. The pintle wire of claim 6 wherein the expandable yarn consists of a synthetic material comprising a blowing agent. 10. The pintle wire according to any one of claims 6 to 9, wherein the external stimulus is heat and the blowing agent is activated by heat. The pintle wire according to any one of claims 6 to 9, wherein the external stimulus is a contact of water and a blowing agent. The pintle wire of claim 1, wherein the expandable filament comprises one or more pre-extended yarns that increase in diameter after longitudinal tension removal. The pintle wire of claim 1, wherein the expandable filament comprises one or more yarns or fibers that absorb water and increase in dimension. 14. The pintle wire of claim 13 wherein said expandable filament comprises a superabsorbent or hydrophilic coating or fibrous sheath on a core filament. The pintle wire of claim 1, wherein the yarn or filament has good abrasion resistance and wear resistant particles or beads are included in the sheath. The pintle wire of claim 10, wherein ferromagnetic filaments are included in the core of the expandable yarn such that induced heat can activate the blowing agent. The pintle wire of claim 1, wherein the wire comprises phosphorescent, luminescent or fluorescent material to assist wire insertion in poor light conditions. Pintle wire according to one of the preceding claims, characterized in that the wire is flattened by rolling. 2. The pintle wire of claim 1, wherein the expandable filament is a bicomponent wire with differential shrinkage between components, the shrinkage of the bicomponent wire increasing the diameter of the filament. The pintle wire of claim 1, wherein the pintle wire has a susceptible polymer sheath that swells upon exposure to water. 21. The pintle wire of claim 20 formed by extruding a yarn from a thermoplastic polymer pellet and coating the yarn with the sensitive polymer sheath. 22. The pintle wire of claim 21, wherein the sensitive polymer is PVA or PEBAX (trade name) and the thermoplastic polymer comprises aliphatic or partially aromatic polyamide and the pellet comprises m- or p-aramid fibers.